Japanese Laid-open Patent Application No. Hei 11-54687 discloses the mounting technology of a surface-mounted semiconductor package by flow soldering. In this mounting technology, first of all, a semiconductor package is tentatively fixed on the main surface of a circuit board with an adhesive. Next, the circuit board is flipped upside down to locate the semiconductor package so as to be facing downward on the circuit board. Then, the semiconductor package and the circuit board are exposed to melted solder so that the external lead of the semiconductor package is soldered with the electrodes of the circuit board. However, in Japanese Laid-open Patent Application No. Hei 11-54687, the semiconductor package may drop when the circuit board is upside down as mentioned above.